Here is a link to the Texas Residential Property Owners Protection Act (Texas's HOA law).
It requires notice to property owners of board meetings, including the general subject of the meeting, but it gives several options for how that notice is to be given. One of those options is to post a notice somewhere in the common areas, or a prominent location on private property within the HOA, at least 72 hours ahead of time. If they did that, you probably didn't see it, if you live in Tennessee.
One avenue of research you can pursue is whether the process the HOA used to make these changes to the rules was itself proper according to the association governing documents. In my HOA, the Board can make changes to the Rules and Regulations, but it takes a supermajority vote of the entire membership to change the Covenants.
Another thing to check into: are you sure you understand exactly what the changes mean? Do the new requirements apply immediately to existing landlord-tenant relationships, or are they intended to kick in the next time a lease comes up for renewal, or even the next time you solicit a new tenant?
If the changes were made using the correct process, and they will put you in an impossible situation where you must choose between violating the HOA rules and violating the lease you signed with your tenant, then I think you have little choice but to consult a Texas real estate attorney knowledgeable about both HOA law and landlord-tenant law.